1. Field of the Invention
The present invention relates to a cooling system for cooling an electric device to be driven by electric power from a battery.
2. Description of the Related Art
FIG. 8 is a configuration diagram illustrating a conventional cooling system for an electric vehicle. In FIG. 8, the conventional cooling system includes a radiator (heat exchanger) 101, a circulating pump 102, a first cooling fluid channel 103A, a second cooling fluid channel 103B, a bypass channel 104, and a valve 105.
The radiator 101 is provided in the second cooling fluid channel 103B. The radiator 101 dissipates heat of a cooling fluid to outside to cool the cooling fluid. The circulating pump 102 is provided in the first cooling fluid channel 103A. The circulating pump 102 applies a pressure for causing the cooling fluid to flow, to the cooling fluid.
The first cooling fluid channel 103A and the second cooling fluid channel 103B are connected to each other to form a circulation channel of the cooling fluid through the radiator 101 and the circulating pump 102. The bypass channel 104 is connected to the first cooling fluid channel 103A in parallel to the second cooling fluid channel 103B so as to bypass the radiator 101.
The valve 105 is provided at a position where the first cooling fluid channel 103A and the bypass channel 104 are connected to each other. The valve 105 switches a direction of the flow of the cooling fluid, which is discharged from the circulating pump 102 to pass through the first cooling fluid channel 103A, between a direction to the radiator 101 and a direction to the bypass channel 104. The switching operation of the valve 105 is controlled by a system control section 150.
A charger 106, an inverter 107, and a motor (electric device) 108 for vehicle running are provided in the first cooling fluid channel 103A. The charger 106 converts AC power received from outside into DC power and charges a battery (not shown) with the DC power. The inverter 107 converts the DC power received from the battery into AC power and supplies the AC power to the motor 108.
The system control section 150 controls the switching operation of the valve 105 according to a temperature of the cooling fluid to switch the direction of the flow of the cooling fluid between the direction to the radiator 101 and the direction to the bypass channel 104. Specifically, when the temperature of the cooling fluid is high, the cooling fluid is guided toward the radiator 101 by the valve 105. In this manner, the heat of the cooling fluid is dissipated by the radiator 101. On the other hand, when the temperature of the cooling fluid is low, the channel is switched by the valve 105 so that the cooling fluid does not pass through the radiator 101. As a result, the cooling fluid is guided toward the bypass channel 104 so that a pressure loss due to the radiator 101 is not generated in the cooling fluid.
The battery of the electric vehicle is charged while the electric vehicle is in a stopped state. At the time of charging, the charger 106 operates, whereas the motor 108 and the inverter 107 do not operate. Moreover, at the time of charging, the circulating pump 102 feeds the cooling fluid to the second cooling fluid channel 103B to cool the charger 106.
Next, FIG. 9 is a configuration diagram illustrating another conventional cooling system for an electric vehicle. The cooling system illustrated in FIG. 9 has a configuration obtained by additionally providing a heater 109 and a heater core 110 in the first cooling fluid channel 103A of the conventional cooling system illustrated in FIG. 8. The heater 109 heats a cooling fluid. The heater core 110 blows warm air into a cabin by using the heated cooling fluid as a heat source.
As the prior art relating to the present invention, there is the one described in Japanese Patent Application Laid-open No. 2008-120244, for example.
In the conventional cooling systems for the electric vehicle as illustrated in FIGS. 8 and 9, the cooling fluid flows into the charger 106 even when the electric vehicle runs. In this manner, the cooling fluid flows even to a device which does not need to be cooled. Therefore, an operation load on the circulating pump 102 becomes large to disadvantageously increase the pressure loss of the cooling fluid. Moreover, with the large operation load on the circulating pump 102, there is a problem in a reduced lifetime of the circulating pump 102.
The problems described above occur not only in the cooling systems for an electric vehicle (EV) and for a hybrid electric vehicle (HEV) but also in a cooling system for an electric system other than a vehicle, which includes a battery, a charger for charging the battery with electric power received from outside, and an electric device to be driven by the electric power of the battery.